微波负载电热耦合的无源互调分析

Passive intermodulation analysis of coupled electro-thermal microwave loads

微波负载可改善电路的匹配性能,吸收微波能量.消耗微波能量产生的焦耳热对微波负载的电阻率产生影响,从而产生无源互调.针对热场与电磁场耦合时导致时间尺度上的差异引起的微波负载无源互调问题,首先利用分数阶微分方法建立了微波负载分数阶热传导模型;然后建立分数阶热传导的电路模型;最后结合热阻效应,推导出微波负载电热耦合引起的无源互调功率电平表达式.分析了材料的电阻温度系数、热阻、热容对无源互调的影响,为微波负载降低电热耦合引起的无源互调提供了参考.

Microwave loads are used to improve the matching performance of circuits and absorb the microwave energy. The microwave loads generate the joule heat to affect the electrical resistivity after consuming microwave energy which may produce the passive intermodulation （PIM）. Electro-thermal compling leads to the difference of the time scale which produces PIM. In order to address the problem, the fractional heat conduction model of microwave loads is created by the fractional calculus firstly. Then the circuit model of the fractional heat conduction is established. Eventually, the thermal resistance effect is considered. The expression for the PIM power level caused by the coupled electro-thermal microwave loads is derived. The influences of the material＇s temperature coefficient of resistance, thermal resistance and thermal capacity to PIM are revealed, which provides the fundamental basis for reducing the PIM from the coupled electro-thermal microwave loads.